1. Field
Example embodiments relate to electromagnetic wave transmission filters. Example embodiments also relate to electromagnetic cameras that may include the electromagnetic wave transmission filters. Additionally, example embodiments relate to filters that may selectively transmit electromagnetic waves of a narrow bandwidth around a certain wavelength and/or electromagnetic cameras including the filters.
2. Description of the Related Art
Recently, electromagnetic cameras, for example, terahertz cameras may have been widely used in various fields, such as, security checking, signal transmission, sample analyzing, and/or medical checkups. In general, electromagnetic cameras may images using electromagnetic waves at radio frequencies in the millimeter or sub-millimeter bandwidth instead of using light (e.g., visible light). In order to obtain an image of a certain wavelength in an electromagnetic camera, an electromagnetic wave transmission filter, that may transmit electromagnetic waves of a certain wavelength, may be disposed on a front portion of an electromagnetic wave detector array.
The electromagnetic wave transmission filter used in the electromagnetic camera may generally be formed with a slit in a metal plate, and/or may have a length that may be smaller than a wavelength of the electromagnetic wave to be transmitted through the electromagnetic wave transmission filter, or a circular opening in the metal plate, having a diameter that may be smaller than the wavelength of the electromagnetic wave. When the slit that may have the length smaller than the wavelength of the electromagnetic wave may be formed in the metal plate, the electromagnetic wave that may have a wavelength twice the length of the slit may be transmitted through the slit. However, in this case, a bandwidth of the wavelength of the electromagnetic wave that may be transmitted through the slit may be relatively large and/or the amount of transmitted electromagnetic wave may not exceed a transmission amount corresponding to a square of the slit area. In addition, when the circular opening that may have the diameter smaller than the wavelength may be formed in the metal plate, a wavelength selectivity of the transmitted electromagnetic wave may decrease and/or the amount of transmitted electromagnetic wave may be reduced in proportion to the fourth power of the diameter of the circular opening.